Ask the Doctors

Dear Doctor: How important is radon as a cause of lung cancer? Should I get my home tested?

Dear Reader: Just a few years ago, radon was the topic of seemingly limitless public and media fascination. Times may have changed, but the presence of radon has not. To answer your question, let's take a closer look at this radioactive element.

A colorless, odorless gas that can be inhaled, radon is produced normally in our environment from the radioactive decay of the elements uranium, radium and thorium. Radon is not a stable element, and its many isotopes are subject to rapid radioactive decay, leading to the release of radioactive particles. This decay also produces solid radioactive elements that can attach to dust particles, which can also be inhaled.

The problem with radon is that exposure to its radioactive particles may lead to cancer, specifically lung cancer. A 2006 study of 59,001 uranium miners followed for 30 years in Germany found a much higher number of lung cancers in those with greater exposure to radon. The highest incidence of lung cancer was seen 15 to 24 years after exposure. Uranium miners in the Colorado Plateau also appear to have an increased risk of lung cancer.

Those who don't mine uranium can't ignore the issue, however. The Iowa Radon Lung Cancer Study, published in 2000, looked at 413 lung cancer cases in Iowa women, ages 40 to 84. The study measured amounts of radon in the homes of those patients who had lived in the same house for more than 20 years. It also measured radon levels in the homes of women with similar ages, smoking histories and work histories who didn't have cancer.

The authors found that 60 percent of the home basements of women with lung cancer exceeded the Environmental Protection Agency limits for radon levels; and 30 percent of the first-floor spaces exceeded those limits. Based on an analysis of radon levels in the control group, the study concluded that increased radon levels led to increased rates of lung cancer.

Subsequently, a combined analysis of 13 European studies evaluated radon levels in the homes of lung cancer patients who had lived there for a minimum of 15 years. For every quantile increase in radon levels, the rate of lung cancer increased by 8.4 percent. Note, however, that smoking played a large part in this increase. When smoking was removed from the equation, the level of increased risk was only 2.3 percent per quantile increase in radon. The authors theorized that, out of all the causes of lung cancer, radon is responsible for 9 percent.

Radon exposure is higher for some people than for others. It enters homes and other buildings through the soil and can build up inside, especially in structures that don't have good ventilation. This is more problematic in winter months when windows are more likely to be closed.

Further, some areas of the country, such as Iowa and the Appalachian Mountains of Pennsylvania, have naturally higher levels of radon. New homes in these areas are constructed to prevent radon from entering and building up inside, and the EPA recommends that all houses be tested. If you're curious about your own area, the EPA has maps showing which zones of the country have more radon.

The take-home message: Radon exposure is considered a substantial risk factor for lung cancer. If you live in a part of the country where radon levels are high, you should have your home tested.